The present invention relates to an improved vehicle wheel construction, particularly bicycle wheels, including an improved connection means for connecting the spokes to the hub.
Heretofore, the vast majority of bicycle wheels have been constructed using steel wire spokes that are connected, at their inner end, to a central hub component and, at their outer end, to a metallic rim hoop. The spokes are generally of steel construction while the hub and rim may be of aluminum or steel construction. The spokes, hub and rim are each formed as separate components that are then joined together with mechanical connections.
To facilitate the assembly of this bicycle wheel, a certain level of automation has been applied to many of the operations. However, several of the operations still require manual labor, such as the tedious process of threading the individual spokes through the hub, a process commonly referred to as xe2x80x9cstuffingxe2x80x9d the hub. After the hub is xe2x80x9cstuffedxe2x80x9d with spokes, the spokes are manually adjusted to align the outer end of the spoke with its corresponding hole in the rim in a process called xe2x80x9clacingxe2x80x9d. The xe2x80x9cstuffingxe2x80x9d and xe2x80x9clacingxe2x80x9d operations have never been automated and are commonly tedious and time consuming tasks which require a relatively high level of skill on the part of the operator.
The manufacture of the hub component is also an expensive process. Some hub shells are machined from billet while others are cast or forged and subsequently machined. This machining operation generally requires at least three machining setups. First the cylindrical portions of the hub are turned on lathe, second, the spoke holes in one hub flange are drilled in a rotary index operation, and third, the opposite hub flange is drilled in a separate rotary index operation as well. This multi-step machining process adds considerable expense to the manufacture of the hub shell component.
The tensile forces within the spoke create high stresses at their connection points and the connection between the spoke and the hub flange must therefore be capable of withstanding these stresses. In the current spoke connection arrangement, stresses due to spoke tension are concentrated within a relatively small region of the hub flange, namely the portion of the hub flange material that is radially outward from the spoke hole. This requires that the hub flange construction be based on expensive, higher strength materials and the use of more expensive forming processes such as forging, rather than less costly processes such as die casting or injection molding. Further, these stresses require that the flange be designed with robust thickness, thus adding weight to the wheel assembly.
The spokes of most conventional wheels are constructed of steel wire with a sharp xe2x80x9cJxe2x80x9d bend close to the headed end and adjacent to the point where they pass through the hole in the flange. The xe2x80x9cJxe2x80x9d bend region of the spoke is considerably weaker and less ductile due to the overstress of the material to achieve this bend. As would be expected, the xe2x80x9cJxe2x80x9d bend region is a common breakage point for spokes of the current design. Spoke manufacturers have attempted to compensate for this shortcoming by thickening the wire in this region, but this solution results in considerable extra expense and weight.
It is often an objective to construct wheels with spokes that are flattened along their length to create a more aerodynamic cross-section profile. With a conventional hub flange, this creates a problem where the extra wide spoke cross section must pass through the round hole in the hub flange. The common assembly method, when flattened spokes are utilized, requires the slotting or notching of each individual spoke hole in the two hub flanges to allow the spoke to pass through. This additional operation adds considerable expense and weakens the hub flange as well.
In recent years, some attempt has been made to improve on this conventional wheel design, but the changes have been minor and still retain the same materials and basic configuration. Interestingly, many of these more modern designs are simply a rehash of inventions that are more than 80 years old. This is likely due to the fact that, aside from some more esoteric examples, these modern wheels rely on similar materials and construction techniques as those employed 80 years ago.
Several recent hub designs have recently been introduced which permit a xe2x80x9cstraight pullxe2x80x9d spoke arrangement where the hub flange includes spoke holes which are in a generally radial direction, thus eliminating the requirement for a xe2x80x9cJxe2x80x9d bend in the spoke. However, since the spoke hole of this new design is in line with the spoke, the spoke has no resistance to spinning within its hole. This can create great difficulty when assembling the wheel, since the opposite end of the spoke includes a threaded connection that requires that the spoke to be fixed in order to facilitate the threaded adjustment. Further, this xe2x80x9cstraight pullxe2x80x9d design does not solve any of the other shortcomings outlined above.
In the past 30 years, there have been significant technological developments in the area of synthetic fibers. Many of these materials have exceptionally high specific tensile properties that are ideally suited for use as the spoke component of the wheel. However, it has proven difficult to adapt these materials to wheel components of a conventional design. The mechanical connections, dictated by current wheel assembly designs, do not allow the present design to take full advantage of these new materials. While some attempts have been made to adapt these materials for use as a spoke, the designs often rely on additional fittings and connections to facilitate their use in wheels of relatively conventional design. A good example of such a design is illustrated in U.S. Pat. No. 4,729,605. These extra fittings add cost and weight to these spokes while the additional connections may compromise the strength of the spoke, thus reducing the potential benefit of these new materials.
Accordingly, it is a principal objective of the present invention to provide a new and improved vehicle wheel construction.
It is a further objective of the present invention to provide a construction as aforesaid which reduces costs and provides a wheel that is light in weight and high in strength and reliability.
Further objects and advantages of the present invention will appear hereinbelow.
In accordance with the present invention, it has now been found that the foregoing objects and advantages may be readily obtained.
The wheel of the present invention comprises: a peripheral wheel rim; a central wheel hub with an outer flange; a plurality of spokes extending between the rim and hub, wherein said spokes have a first outer peripheral portion connected to said rim and a second inner portion opposed to said first portion; with at least one of the first portion and the second portion of at least one spoke secured to at least one of said rim and hub by hardened molding material which is integral or solid connected with the rim and hub, respectively and preferably adhered or bonded thereto, and wherein the hardened molding material has a surface conforming to a surface of the rim and hub, respectively. The second portions of the spokes are desirably secured to said outer flange and desirably are encapsulated in said hardened molding material. Preferably, a plurality of spokes are so secured and desirably there is a joining interface between the spokes and hardened molding material. The hardened molding material will preferably form at least a portion of a flange. The hardened molding material encapsulates the spoke or spokes and preferably surrounds the entire cross-section thereof.
The present invention obtains many advantages. An integral firm connection is obtained and not simply a mechanical connection. It is an advantage of the present invention that costs are reduced by reducing the assembly labor required to build a wheel. During manufacture, the spokes of the present invention need only to be placed in the intended location prior to the hub flange being formed or molded around them. This eliminates the inherently manual operation of threading each individual spoke through its mating hole in the hub flange and greatly simplifies the operation of xe2x80x9cstuffingxe2x80x9d the hub and greatly reduces the amount of labor required for this operation. Further, due the simplicity of this manufacturing operation, the opportunity exists to utilize factory automation techniques and/or robotics to perform this operation, thus further reducing manufacturing costs.
After the hub flange material of the present invention is formed around the spokes, a spoke xe2x80x9cspiderxe2x80x9d is now produced with spokes that are xe2x80x9cprefixturedxe2x80x9d and locked in fixed relation to the hub flange and directed toward the rim at the optimum angle designed into the assembly. This spoke spider is now one individual component that is far easier to handle as compared with the clumsy loosely connected assembly associated with conventional wheels. This eliminates the manual spoke alignment operation, where the individual loose spoke of a conventional wheel assembly are manually directed toward their corresponding attachment hole in the rim.
An additional advantage of the present invention is the reduction in cost through the ability to utilize inexpensive and efficient manufacturing techniques in the production of component parts.
The hub and hub flange of the present invention may be produced using xe2x80x9cnet shapexe2x80x9d molding techniques which reduce or eliminate the need for expensive machining operations. Since this design is well suited to such molding or casting operations, the desired hub geometry may be produced with few, if any, secondary machining operations. In the case where subsequent machining is required, far fewer of these costly operations are anticipated than if the hub were produced from a billet or a forging. Further, in such a xe2x80x9cnet shapexe2x80x9d forming operation, the amount of material waste is greatly reduced, particularly when compared to a part that is fully machined from billet.
Since the spoke tension stresses of the present invention are distributed over a wider region of the hub flange interface, stresses are reduced within the hub flange material. Thus the strength requirements for the hub flange material are reduced and lower performance materials may be utilized, further reducing the cost as compared with conventional hubs. For example, the hardened molding material and the hub flange of the present invention may now be formed from relatively inexpensive polymer resins. These materials also lend themselves to lower-cost forming operations such as plastic injection molding. If a metallic hub flange is deemed necessary, high strength billet alloys are no longer required. Lower strength metal casting alloys, which may be formed using a casting process such as die-casting, will likely have sufficient strength.
Also, fiber reinforced injection molding compounds may now be utilized in the present invention. With these high strength composite polymers, the injection molding process permits the fibers to attain a generally random orientation within the matrix. This is a significant benefit that would not apply if the hub were machined from a fiber reinforced plastic billet. Fiber reinforced billet is normally produced by an extrusion process where the fibers become highly aligned in the direction of extrusion. Thus, a hub shell machined from such a billet would have relatively low strength perpendicular to the direction of extrusion.
Spokes of non-circular geometry, such as flat spokes, may be easily adapted to the present invention since the hub flange material is now conformed to the spoke. This is a shortcoming of conventional wheels since they are almost exclusively assembled with spokes of round cross-section. This is because the flanges must be machined to accept the spoke and it is far easier to machine a round hole than an oblong hole. Hardened molding material may create a structural portion of the hub shell or flange. The hardened molding material may also provide a matrix including reinforcement fibers or particles which impart improved mechanical properties to the solidified material.
Many of the embodiments of the present invention also illustrate the ease with which duplex spokes may be incorporated into the present invention. These duplex spokes create the equivalent of two individual spokes using only a single series of manufacturing operations and are thus less expensive to produce.
The spokes of a conventional wheel are each produced as single components and require very specific and accurate geometry to mate with the conventional hub flange. However, the spokes of the present invention are easier to produce. In many cases, manufacturing operations such as the bending or heading of the spokes are eliminated, thereby reducing the expense. Also, since the hub flange material is now formed to conform to the spoke, much of the accuracy in the spoke geometry is no longer required.
An additional advantage of the present invention is the production of a wheel which is light in weight and high in strength and reliability.
In an effort to enhance the performance of the bicycle, designers have continually aimed toward reducing the weight of its components while maintaining the strength and reliability that the marketplace requires. This is particularly true of the rotating components, such as the wheel, since any weight reduction reduces the rotational inertia as well as the static mass of the bicycle.
Due to its relaxed strength requirements, the present invention permits the use of lightweight materials to produce the hub flange component. Thus, materials such as polymers, reinforced polymers, magnesium, aluminum, among others, may now be used to construct the hub flange, saving precious weight.
Additionally, since the present invention permits the use of net-shape molding operations, the hub flange may be produced to include far more intricate geometry than would be realistic for a hub that is machined from billet. This allows the designer to eliminate material from the hub flange in the locations where it is not required, further saving precious weight.
Further, the spokes of the present invention are readily adaptable to utilize many of the high strength fibers presently available. Since the hub surrounds the fiber spoke, the spoke material may be held firmly in place in direct connection to the hub flange, thus eliminating the requirement for additional fittings or connection to adapt the spoke.
Many of the embodiments of the present invention illustrate the use of additional preformed components incorporated within the overmolding hub flange material. This allows additional components such as a preformed reinforcement or a preformed intermediate connection member to be incorporated into the design. Thus, the hub shell may be of hybrid construction and composed of several components, where each component is made from a material that particularly suits its function. For example, this allows the designer to locate components made from higher strength materials specifically where they are needed to achieve the greatest structural efficiency with the minimum weight.
As illustrated in many of the embodiments of the present invention, the J-bend of traditional spokes may be eliminated with the present invention, thereby eliminating a region where the spoke material is highly stressed and prone to failure.
Due to fabrication methods employed in conventional hub construction, it is very difficult to machine or otherwise create the details required to insure that the geometry of the hub flange conform to the spoke surface without any clearances. Such clearances allow flexure or-movement under tensile loading of the spoke, creating inconsistent spoke tension. Further, it is common practice for the builder of conventional wheels to manually bend the spokes in an attempt to conform the spoke to the hub flange and align the spoke in its direction toward the rim. This is obviously a compromise since, particularly in the case of bicycle wheels, the rim is of relatively light construction and any inconsistency in spoke tension or spoke flexure characteristics will cause the wheel to go out of true, or worse, will cause spoke breakage. When the tensile loads are not evenly shared by all of the spokes, the spokes with greater stresses will be more prone to breakage as will the portions of the rim and hub flange associated with these spokes.
The encapsulated spoke connection of the present invention results in a hub flange that fully conforms to the geometry of the spoke creating a firm connection. Therefore, the spoke tensile loads produce no relative movement between the spoke and the hub flange. The exposed portion of the spoke extends to its connection at the rim in a straight and aligned direction. Thus spoke tensile forces may now be evenly shared among the spokes of the wheel, resulting in a stronger, more reliable wheel that is less prone to broken components and is far more effective at maintaining trueness and rim alignment.
The wheel of the present invention is far less prone to broken components, particularly the spoke components. The spokes may now be permanently affixed to the hub and it will be unlikely that they will require individual replacement over the life of the wheel. This greatly simplifies the manufacturing requirements for this wheel and also reduces maintenance requirements for the end user.
Further objects and advantages of the present invention will become apparent from considering the drawings and ensuing description.